This present application relates generally to apparatus and systems for improving the efficiency, performance and/or operation of combustors in combustion turbine engines. More specifically, but not by way of limitation, the present application relates to apparatus and systems for improved air inlets, air filters and/or flow conditioners within combustors. (Note that, while the present invention is presented below in relation to one of its preferred usages within the combustion system of a power generating combustion turbine engine, those of ordinary skill in the art will appreciated that the usage of the invention described herein is not so limited, as it may be applied to other types of combustion turbine engines.)
Those of ordinary skill in the art will appreciate that combustion turbine engines may operate combustors that include microchannel fuel injectors. A microchannel fuel injector is so named because it introduces the fuel/air mixture through a series of small channels. These types of fuel injectors are effective at delivering a desired flow of pre-mixed fuel to the combustion chamber and provide performance advantages in certain applications as well as allowing flexibility as to the type of fuel the engine is able to burn. However, this type of fuel injector, which will be referred to herein as a “microchannel fuel injector”, is susceptible to blockage from small particles that may be contained in the stream of compressed air that the compressor supplies to the combustor. That is, the microchannels may become clogged by small particles that, in most conventional fuel injectors, would have not been problematic. Such clogging generally results in poor engine performance and may cause significant damage to the fuel injector and the combustion system. In some cases, the blockage actually results in the flame traveling into the fuel injector from the combustion chamber, which may damage the injector.
As a result, combustors that include microchannel injectors typically provide a filter upstream of the injectors for removing particles that may block the microchannels. It will be appreciated that this filter generally consists of a screen positioned over openings or “windows” formed through the cap assembly. Because of the small size of the particles that must be captured, the screen must have a fine mesh. This, of course, means that the screen has a large blockage ratio, i.e., the screen mesh blocks a large portion of the window area through which the air entering the combustor must flow. Blockage ratios of 50% or more are common in the screens that are used in these types of filtering applications. In addition, the windows within the cap assembly are limited in size. It will be appreciated that this forward area of the cap assembly provides the structural support to the aft areas of the cap assembly, as the cap assembly essentially is cantilevered in an aftwise direction from the connection it makes with the endcover.
The combination of these necessary design restraints, i.e., the fine mesh of the screen and the limited window area, result in an effective flow area that is restrictive given the supply of air that must pass therethrough. That is, the conventional screen/window configuration, which, as discussed in more detail below, generally includes a finely meshed screen placed directly over the windows) results in an effective flow area that causes a relatively high-pressure drop, which, of course, negatively affects engine performance. As a result there is a need for a more effective configuration to this area of the combustion. Such improvement should provide a larger effective flow area through the forward area of the cap assembly while also still maintaining the necessary structural support to the unit. In addition, a successful improvement should be cost-effective in production and installation, and be able to be retrofit into operating combustion turbines. The any such improvement should be flexible in operation. That is, the improvement should operate under a variety of conditions and with different sorts of fuel. Further, a filtering element that provided enhanced aerodynamic performance characteristics while being durable and cost-effective in implementation would satisfy a significant need within the field.